1. Field of the Invention
The present invention relates generally to camera shutters and, more specifically, to a focal-plane shutter having shutter sectors for carrying out an exposure operation during use of the camera.
2. Description of the Related Art
Generally, a focal-plane shutter for a camera is arranged so as to cover a film surface by opening sectors before operation of the shutter and by closing sectors after operation of the shutter. In either case, when a rear cover of the camera is opened, as shown in FIG. 7, either of the opening and closing shutter sectors are exposed.
The focal-plane shutter is generally arranged immediately before the film surface. Accordingly, there are cases in which the shutter sectors are contacted directly by the hand of the camera user when the rear cover of the camera is opened to remove a photographed roll of film or to load a new roll of film. As a result of this direct contact, the shutter sectors may be subjected to deformation or breakage, or may even be inadvertently pushed into the camera, which renders the shutter sectors, and thus the focal-plane shutter, non-operational.
In view of the foregoing disadvantage of the prior art, it is an object of the present invention to provide a focal-plane shutter for a camera in which direct contact with shutter sectors by the camera user is prevented. According to the present invention, the shutter sectors of the focal-plane shutter are evacuated from an opening portion of the camera when a rear cover of the camera is opened to prevent direct contact with the shutter sectors through the opening portion by the camera user, thereby preventing an abnormal operation of the focal-plane shutter.
The foregoing and other objects of the present invention are carried out by a focal-plane shutter which executes an exposure operation by successively operating an opening sector group and a closing sector group each having a plurality of shutter sectors. The focal-plane shutter comprises a base plate for connection to a body of a camera having a rear cover which can be opened and closed, such as during a film replacement operation. The base plate has a shutter opening. An opening sector group has a plurality of sectors for undergoing opening movement in an operational state to open the shutter opening during a shutter release operation. A closing sector group has a plurality of sectors for undergoing closing movement in an operational state to close the shutter opening during the shutter release operation. The focal-plane shutter further requires control means for controlling the opening sector group and the closing sector group to open and close the shutter opening, respectively, and holding means for holding the closing sector group at a nonoperational position during an opening state of the rear cover of the camera and for releasing the hold of the closing sector group in the nonoperational position during a closing state of the rear cover of the camera.
In another embodiment, the focal-plane shutter has a construction such that when the rear cover of the camera is opened before setting the shutter, the opening sector group is operated after setting the shutter by operating a motor built in the camera. More specifically, the opening sector group is operated by the motor when the motor is setting the shutter. After such setting of the shutter, the opening sector group is operated by a spring. When a charge member is operated by the motor, a set lever is operated by the charge member, and an opening drive lever is operated by the set lever 1. The opening sector group is then operated by the opening drive lever. Alternatively, the focal-plane shutter may have a construction such that before setting the shutter, the rear cover of the camera is brought into a nonoperational state.
According to the present invention, when rear cover of the camera is opened, a switch provided in a camera main body is closed, electricity is conducted to electromagnets and motion of the opening sector group and the closing sector group is constrained. At the same time, a holding lever is made pivotable to thereby hold the closing sectors and constrain operation thereof. Thereafter, electricity conduction to the electromagnets is cut and the opening sector group is evacuated from a shutter opening. The closing sector group is not operated since the closing sector group is held by the holding lever. Therefore, when the rear cover is opened, there is brought about a state in which both of the opening sector group and the closing sector group are evacuated from the shutter opening.